Three scientists will win this year's Nobel Prize in Physiology or Medicine for their role in figuring out how cells talk to one another. They do that by releasing and soaking up molecules. This basic knowledge also helps explain diseases, from mental illness to immune disorders.

NPR's Richard Harris has our story.

RICHARD HARRIS, BYLINE: Jim Rothman started his career studying physics and when he changed course and decided to go to medical school, he says he still tended to think of living things as machines. One day, he heard a lecture that started to get into the basic mechanics of how living cell manages to package up and secrete chemicals such as hormones.

JIM ROTHMAN: It was a complete mystery how that could happen at a molecular level. And so, when I had the opportunity and was prepared to take the risk, that's what I decided to focus on.

HARRIS: These secretions are everywhere you look; pancreas cells secrete the hormone insulin to help you digest and nerve cells in the brain secrete chemicals called neurotransmitters to talk to one another.

ROTHMAN: One of the less heralded but absolute secretory products are the endorphins, which cause a good mood. Now, everybody has commented on how my mood has been very good today.

(LAUGHTER)

HARRIS: At a Yale University news conference celebrating his Nobel Prize this afternoon, Rothman credited his great mood to the endorphins his cells are secreting, along with dopamine, which is secreted in the brain's reward circuitry. His point, of course, is that our bodies rely on all these secretions. When something goes awry, diseases can often result, as varied as autism, Alzheimer's and even our body's toxic reaction to botulism.

Rothman says he's very grateful he started this work in the early 1970s, back when the federal government was willing to take much bigger risks in handing out funding to young scientists.

ROTHMAN: I had five years of failure, really, before I had the initial sign of success. And I'd like to think that that kind of support existed today, but I think there's less of it. And it's actually becoming a pressing national issue, if not an international issue.

HARRIS: And while Rothman attacked this problem by trying to understand the mechanics of secretions, Randy Schekman decided to see what he could understand by studying the genes. He picked a simple organism, yeast, to study. Today, he's a Howard Hughes Medical Institute investigator at UC Berkeley.

RANDY SCHEKMAN: One starts off just interested in basic science. I had no inkling that this would have any practical application. But more often than not, what one does in the laboratory can be applied.

HARRIS: In fact, once Schekman started to understand how these yeast genes worked, he helped a pioneering biotech company called Chiron to custom-make yeasts to secrete medications.

SCHEKMAN: The world's supply of vaccine for hepatitis B is actually made in yeast. And then they harvest yeast cells to manufacture and secrete insulin, which is now one-third of the world supply of human insulin is made by secretion in yeast.

HARRIS: Schekman and Rothman, working independently, gradually started to realize that their two stories were coming together. The genes in yeast were very much like the same genes in animals, so it was two complementary ways of uncovering the same basic story.

SCHEKMAN: We were comparing notes all along, sometimes collaboratively, we actually published papers together, sometimes competitively.

HARRIS: And the whole line of research started building huge momentum. Among the scientists attracted by this problem was German-born Tom Sudhof. He has dedicated his career to learning how nerve cells in the brain fine-tune their secretions in order to communicate with one another.

TOM SUDHOF: It is absolutely crucial to understanding diseases such as Alzheimer's disease on the one hand and autism on the other hand.

HARRIS: He's now a Howard Hughes scholar at Stanford University and he will share the $1.2 million prize with Schekman and Rothman.